Radio frequency identification (RFID) chips typically include circuitry that rectifies a carrier wave to generate a regulated power supply for the chip. The carrier wave is generated by an RFID chip reader and received by an antenna of the RFIS chip. The further the reader is from the RFID chip, the weaker the carrier wave is when it reaches the RFID chip. Consequently, the further the reader is from the RFID chip, the lower the voltage and the amount of power available to the chip from the rectified carrier wave. In order to achieve the longest possible read distance, RFID chips are designed to operate at the lowest possible voltage. The RFID chips can operate at less than 2 Volts.
Often the rectifying circuitry includes a pair of diodes for achieving the rectification. Each diode has a characteristic forward voltage drop. The forward voltage drop is the voltage drop as current passes through the diode when the diode is forward biased. These forward voltage drops can be 700 mV to 800 mV. Taking these voltages drops into account, the maximum operating voltage achievable by the rectifying circuitry is the peak-to-peak voltage on the antenna less the sum of the forward voltage drops of the rectifying diodes. Since the operating voltage of an RFID chip can be less than 2 Volts, the forward voltage drops of the rectifying diodes can account for a significant portion of the peak-to-peak voltage received by the RFID chip antenna.